1. Field of the Invention
The present invention relates to an incident-light fluorescent illumination device and a fluorescent microscope using the device.
2. Description of the Related Art
Recently, in the field of an illumination device for a microscope, an illumination device provided with a fly-eye lens is proposed for a configuration of the conventional Koehler illumination.
Since a fly-eye lens can suppress the uneven illumination caused by the angle dependence (hereinafter referred to as light distribution angle characteristic) of the quantity of light emitted from a light source, which has been difficult in the conventional Koehler illumination, it effectively contributes to the improvement of the uniformity of illumination.
The illumination device of a microscope provided with a fly-eye lens is disclosed by, for example, Japanese Laid-open Patent Publication No. 2005-283879. The illumination device disclosed by Japanese Laid-open Patent Publication No. 2005-283879 is an incident-light fluorescent illumination device, and relays a plurality of light source images formed by the fly-eye lens (converging lens array) to the pupil position of an objective. That is, the position of the light source image and the pupil position of the objective have an optically conjugate relation, and realize the Koehler illumination. Thus, telecentric illumination can be realized, and the uniformity of illumination can be improved using the fly-eye lens.
In a microscope, the pupil position of an objective depends on various factors such as the switching of objectives etc. In the conventional illumination device, the conjugate relation between the position of a light source image and the pupil position can be maintained by moving the light source with a change of the pupil position.
On the other hand, in the case of the illumination device disclosed by Japanese Laid-open Patent Publication No. 2005-283879, since the positional relation between the light source and the fly-eye lens cannot be changed, the conjugate relation between the position of the light source image and the pupil position can be maintained by moving the entire optical system from the light source to the fly-eye lens.
By considering that the magnification at which the light source image formed by a fly-eye lens is projected onto the pupil position of the objective is lower than the magnification at which the light source is projected onto the pupil position of the objective by the conventional incident-light fluorescent illumination system without a fly-eye lens, the necessary amount of movement of an optical system to maintain the conjugate relation is larger than the amount of movement of the conventional light source.
Furthermore, the pupil position of an objective also depends on the configuration of the microscope provided with an illumination device in addition to the switching of an objective. The change of a pupil position caused by the difference in configuration of a microscope is larger than the change normally caused by the switching of objectives.
For example, when a microscope whose nose-piece (nose-piece) moves in the optical axis direction (hereinafter referred to as a moving-nose-piece microscope) is compared with a microscope whose stage moves (hereinafter referred to as a moving-stage microscope), the moving-nose-piece microscope is longer in distance from the light source to the pupil position of the objective. Since the moving-nose-piece microscope has to keep a sufficient distance between the stage and the objective by the movement of the nose-piece when a sample is put on the stage, it is necessary to provide space for saving the nose-piece on the light source side of the nose-piece. Since the length of the space in the optical axis is to be normally 1 through 1.5 times longer than the parfocalizing distance, the distance between the pupil position of the objective of moving-nose-piece microscope and that of the moving-stage microscope is 1 through 1.5 times longer than the parfocalizing distance. That is, by the difference in configuration of the microscope, there occurs a change in pupil position of the objective by 1 through 1.5 times longer than the parfocalizing distance.